How to remove a common prefix from vertex-group names?
To remove the "b_" prefix

import bpy
obj = bpy.context.active_object
prefixes = ["b_", "f_", "h_", "x_"]

bpy.ops.object.mode_set(mode='OBJECT',toggle=True)
for g in obj.vertex_groups:
    for prefix in prefixes:
        if g.name.startswith(prefix):
            g.name = g.name[2:]